1. Technical Field
The present invention relates to Signaling System 7 (SS7/C7) networks and, more particularly, to a mapping function and method for transmitting signaling messages from a first licensed operator network to a second licensed operator network, where both operator networks use the same national numbering plan to assign point codes identifications.
2. History of Related Art
The evolution of telecommunication networks has resulted in a need today for using international gateways, Global Title databases and Point Code databases that require complex and precise inter-working coordination between rival licensed operator networks to ensure the proper delivery of signaling messages.
As is known in the art, network nodes route SS7/C7 signaling messages within the SS7/C7 network and manage the various signaling links which comprise the SS7/C7 network. Routing is accomplished by processing a routing label of the SS7/C7 signaling message by a Message Transfer Part (MTP) functionality of a signaling point (SP). The MTP comprises three levels. Levels 1 and 2 facilitate the transfer of signaling messages from one point to another point over an individual signaling link. Level 3 facilitates the transfer of signaling messages over SS7/C7 networks beyond the requirements of the individual signaling links. In other words, levels 1 and 2 are concerned with transport over individual links whereas level 3 is concerned with transport over SS7/C7 network in general.
A node accomplishes its routing task at level 3 through the use of point codes, which identify the various signaling points in the network. The MTP level 3 of the node identifies the destination point code in the signaling message and selects the proper signaling link for routing that message. For example, if node A sends a signaling message to node B through a Signaling Transfer Point (STP), the message contains the origination point code for the signaling point in node A and the destination point code for the signaling point in node B. The STP accepts this message from one signaling link, reads the destination point code, and places the message on the appropriate link for node B.
Based on that, rival licensed operator networks, in order to exchange signaling messages, need to interconnect their SS7/C7 networks using gateways and complex inter-working configuration management schemes such as Global Titles or Point Codes, which requires a complex inter-working coordination to ensure proper delivery of signaling messages. This complex inter-working coordination between the operator networks increases the risk of inaccuracies during the definition of the Point Code databases. Such inaccuracies may result in Point Code conflicts for many operators and cause problems such as circular routing (signaling message routing continuously back and forth) due to duplication of Point Codes For example, this problem occurs when the operator network defines a node with a Point Code which is already used by another node within the same operator network or a rival operator network thus resulting in incorrect routing information. The incorrect routing information causes each processed signaling message to be routed repeatedly between nodes with the same Point Code without reaching its final destination. This circular routing condition continues indefinitely and may lead to network congestion and possible failure within the network.
Repeating Point Codes are also dangerous. For one thing, any one node cannot route towards two different nodes, which use the same Point Code. But worse, if one such node fails, all its neighbors will broadcast management messages (such as, Transfer Prohibited, TFP) which will be sent throughout both networks and stop all signaling to both the failed node and the healthy node.